Sn / ge halide nanocrystal and sn / ge halide nanocrystal composite, method for producing sn / ge halide nanocrystal, fluorescent substance, fluorescent material, and resin sheet

Abstract

Provided is a Sn / Ge halide nanocrystal represented by general formula (1): Cs3(Snα1Ge(1-α1))(Brβ1I(1-β1))5, wherein α1 is 0.00-0.40 and β1 is 0.00-1.00. According to the present invention, it is possible to provide a novel lead-free halide nanocrystal and lead-free halide nanocrystal composite having a high photoluminescence quantum yield and exhibiting a peak of emission from red to near infrared wavelengths.

Description

Sn / Ge halide nanocrystals and Sn / Ge halide nanocrystal composites, method for producing Sn / Ge halide nanocrystals, phosphor, fluorescent material, and resin sheet

[0001] The present invention relates to Sn / Ge halide nanocrystals and Sn / Ge halide nanocrystal composites, methods for producing them, phosphors, fluorescent materials, and resin sheets.

[0002] Lead halide perovskite nanocrystals have attracted attention as next-generation luminescent materials due to their high luminescence quantum yield and the ability to control the emission wavelength in the visible light region. However, because they contain toxic lead, there is a need to develop halide perovskite nanocrystals using elements with a lower environmental impact.

[0003] For example, Non-Patent Document 1 describes tin halide perovskite nanocrystals, which were synthesized for the first time in 2016 by the hot injection method, as a halide perovskite nanocrystal using elements with a low environmental impact. However, these nanocrystals have issues such as an extremely low luminescence quantum yield and poor stability due to the oxidation of tin.

[0004] Furthermore, for example, Non-Patent Document 2 reports that germanized nanocrystalline perovskite crystals using germanium, which is an element belonging to Group 14 like tin, were synthesized by the hot injection method in 2018. However, as with tin, the difficulty of suppressing the oxidation of germanium is an issue.

[0005] Furthermore, when considering the application of tin halide perovskite nanocrystals to agriculture, medicine, and beauty, the emission wavelength range was also an issue.

[0006] For example, it is generally known that the absorption wavelength range of chlorophyll a, the main photosynthetic pigment in plants, is red light (wavelength range of approximately 620 to 700 nm) with a peak at 660 nm.

[0007] Furthermore, near-infrared light in the 700-1000 nm range is known to be effective in preserving the freshness of vegetables by improving their antioxidant activity (Agricultural Technology System: Fruit Trees, 2021 Edition).

[0008] Furthermore, if it becomes possible to excite within a biological window using red light of 650 nm, it will be possible to aim for higher image resolution and reduced side effects by reducing the amount of drugs used in applications to biomarkers.

[0009] TC Jellicoe et al,. J. Am. Chem. Soc 2016 138. 2941-2944X. Wu, et al,. Chemistry-An Asian Journal. 2018. 13. 13. 1654-1659

[0010] Until now, there have been no materials that satisfy the luminescence quantum yield (PLQY) and emission wavelength range required for these applications. Perovskite nanocrystals generally have a wide range of emission wavelengths that can be controlled by changing the chemical composition and crystal size. For example, Pb ２＋ Sn with a smaller ion size ２＋ Although it is possible to increase the wavelength of the light emitted to near-infrared light of 800 to 950 nm by replacing the light with , there is a problem that the light emission quantum yield is extremely low at 1% or less.

[0011] Furthermore, the peak emission wavelength of existing tin halide nanocrystals is 600 nm, and there is a problem in that the peak emission wavelength needs to be extended to a longer wavelength when considering application to plant cultivation.

[0012] To expand these applications, there was a need to develop high-performance, lead-free halide nanocrystals that have a high luminescence quantum yield and an emission wavelength peak in the red to near-infrared region.

[0013] Therefore, an object of the present invention is to provide novel lead-free halide nanocrystals and non-lead halide nanocrystal composites that have a high luminescence quantum yield and an emission wavelength peak in the red to near-infrared region, and to provide fluorescent materials and resin sheets that use novel lead-free halide nanocrystals and non-lead halide nanocrystal composites that have a high luminescence quantum yield and an emission wavelength peak in the red to near-infrared region.

[0014] The object of the present invention is achieved by the following invention: That is, the present invention (1) provides a compound represented by the following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00).

[0015] The present invention (2) also provides a Sn / Ge halide nanocrystal composite, characterized by comprising the Sn / Ge halide nanocrystal of (1) and a ligand bound to the Sn / Ge halide nanocrystal, wherein the ligand has a lipophilic molecular chain and / or a hydrophilic molecular chain and a binding group.

[0016] The present invention (3) also provides a phosphor characterized by comprising the Sn / Ge halide nanocrystals of (1).

[0017] The present invention (4) also provides a fluorescent material characterized by containing the Sn / Ge halide nanocrystals of (1) or the Sn / Ge halide nanocrystal composite of (2).

[0018] The present invention (5) also provides a fluorescent material characterized in that the surface of the phosphor of (3) or the fluorescent material of (4) is coated with a light-transmitting resin.

[0019] The present invention (6) also provides a resin sheet comprising a light-transmitting resin substrate and containing the phosphor of (3) or the fluorescent material of (4).

[0020] The present invention (7) also provides a method for producing a cesium precursor represented by the following general formula (1): Cs by a hot injection method in which a solution obtained by mixing tin bromide and / or tin iodide and germanium bromide and / or germanium iodide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted. ３ (Sn α１ Ge （１－α１） ) (Br β１ I（１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), a nanocrystal synthesis step (A) is provided to obtain Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00, and in all raw materials mixed in the nanocrystal synthesis step (A), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, and the molar ratio of Br to the total of Br and I (Br / (Br+I)) is 0.00 to 1.00, on an atomic basis.

[0021] The present invention (8) also provides a method for producing a compound represented by the following general formula (2): Cs by a hot injection method in which a solution obtained by mixing tin bromide and germanium bromide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted. ３ (Sn α２ Ge （１－α２） )Br ５ (2) (wherein α2 is 0.00 to 0.40), a nanocrystal synthesis step (B) of obtaining Sn / Ge halide nanocrystals represented by the general formula (2) and a salt of a metal cation or an organic cation and an iodine anion, and a halogen substitution reaction is carried out to obtain a Sn / Ge halide nanocrystal represented by the general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５(1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (C) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in the nanocrystal synthesis step (B), the molar ratio of Sn to the total of Sn and Ge, on an atomic basis (Sn / (Sn+Ge)), is 0.00 to 0.40; and in the halogen substitution step (C), the ratio (I / Br) of the number of moles of I, on an atomic basis, in a salt of a metal cation or an organic cation and an iodine anion to the number of moles of Br, on an atomic basis, in the Sn / Ge halide nanocrystals represented by the formula (2), is 0.00 to 5.00.

[0022] The present invention (9) also provides a method for producing a cesium precursor represented by the following general formula (3): Cs by a hot injection method in which a solution obtained by mixing tin iodide and germanium iodide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted. ３ (Sn α３ Ge （１－α３） ) I ５ (3) (wherein α3 is 0.00 to 0.40), a nanocrystal synthesis step (D) of obtaining Sn / Ge halide nanocrystals represented by the general formula (3) and a salt of a metal cation or an organic cation and a bromine anion, and by a halogen substitution reaction, obtaining Sn / Ge halide nanocrystals represented by the general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５(1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (E) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in the nanocrystal synthesis step (D), the molar ratio of Sn to the total of Sn and Ge, on an atomic basis (Sn / (Sn+Ge)), is 0.00 to 0.40; and in the halogen substitution step (E), the ratio (Br / I) of the number of moles of Br, on an atomic basis, in a salt of a metal cation or an organic cation and a bromine anion to the number of moles of I, on an atomic basis, in the Sn / Ge halide nanocrystals represented by the formula (3), is 0.00 to 5.00.

[0023] According to the present invention, it is possible to provide novel lead-free halide nanocrystals and non-lead halide nanocrystal composites that have a high luminescence quantum yield and an emission wavelength peak in the red to near-infrared region. Also, according to the present invention, it is possible to provide fluorescent materials and resin sheets that use novel lead-free halide nanocrystals and non-lead halide nanocrystal composites that have a high luminescence quantum yield and an emission wavelength peak in the red to near-infrared region.

[0024] 1 is a schematic diagram showing the structure of the Sn / Ge halide nanocrystals of the present invention. 2 is an image of the reaction mother liquor in Examples 1 and 2. 3 is a schematic diagram showing the structure of the Sn / Ge halide nanocrystals of the present invention. ３ (Sn α Ge （１－α） ) (Br β I （１－β） ) ５ PL spectrum and PLQY of Cs in Example 3 ３ (Sn ０．１ Ge ０．９ ) I ５ TEM image of Cs in Example 3 ３ (Sn ０．１ Ge ０．９ ) I ５ PL spectrum and PLQY of Cs in Example 4 ３ (Sn ０．１ Ge ０．９ ) (Br ０．８２ I ０．１８ ) ５ PL spectrum and PLQY of powdered Cs ３(Sn α Ge （１－α） ) (Br β I （１－β） ) ５ Image of powdered Cs ３ (Sn α Ge （１－α） ) (Br β I （１－β） ) ５ PL spectrum and PLQY of powdered Cs ３ (Sn α Ge （１－α） ) (Br β I （１－β） ) ５ PL spectrum of the atmospheric stability of powdered Cs ３ (Sn α Ge （１－α） ) (Br β I （１－β） ) ５ UV-vis absorption spectrum of powdered Cs ３ (Sn α Ge （１－α） ) (Br β I （１－β） ) ５ Images of changes over time and PLQY.

[0025] The Sn / Ge halide nanocrystals of the present invention are represented by the following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00).

[0026] 1 is a schematic diagram showing the Sn / Ge halide nanocrystals of the present invention. The Sn / Ge halide nanocrystals of the present invention are generally ３ BX ５The Sn / Ge halide nanocrystals of the present invention are nano-sized crystals of a Sn / Ge halide compound having the structure shown in Figure 1, represented by the formula: The Sn / Ge halide nanocrystals of the present invention are Sn / Ge halide compounds in which the A-site element is Cs, the B-site element is Sn and / or Ge, and the X-site element is Br and / or I. In other words, the Sn / Ge halide nanocrystals of the present invention are lead-free halide nanocrystals.

[0027] The Sn / Ge halide nanocrystals of the present invention are Sn / Ge halide nanocrystals represented by general formula (1), which emit light in the red to near-infrared region. In particular, the Sn / Ge halide nanocrystals of the present invention are novel Sn / Ge halide nanocrystals that are different from conventional nanocrystals and have previously unobtainable fluorescent properties, such as peak emission wavelengths at higher wavelengths in the red or near-infrared region than conventional nanocrystals. Specifically, they exhibit peak emission wavelengths at wavelengths longer than 600 nm, resulting in emission over a narrower band. Furthermore, because the Sn / Ge halide nanocrystals of the present invention are Sn / Ge halide compounds represented by general formula (1), they have a high luminescence quantum yield (PLQY) and exhibit peak emission wavelengths at wavelengths longer than 600 nm, preferably at 620 nm or longer.

[0028] In general formula (1), α1 is 0.00 to 0.40, preferably greater than 0.00 and equal to or less than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. That is, the molar ratio of Sn to the total moles of Sn and Ge at the B site in the Sn / Ge halide nanocrystal of the present invention is 0.00 to 0.40, preferably greater than 0.00 and equal to or less than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. By setting the value of α1 within the above range, the peak emission wavelength of the Sn / Ge halide nanocrystal can be shifted to a longer wavelength.

[0029] In general formula (1), β1 is 0.00 to 1.00, preferably greater than 0.00 and less than 1.00, more preferably 0.05 to 0.95, more preferably 0.10 to 0.90, more preferably 0.20 to 0.80, and more preferably 0.30 to 0.70. That is, the molar ratio of Br to the sum of Br and I at the X site in the Sn / Ge halide nanocrystal of the present invention is 0.00 to 1.00, preferably greater than 0.00 and less than 1.00, more preferably 0.05 to 0.95, more preferably 0.10 to 0.90, more preferably 0.20 to 0.80, and more preferably 0.30 to 0.70. By setting the value of β1 within the above range, the peak emission wavelength of the Sn / Ge halide nanocrystal can be shifted to a longer wavelength.

[0030] The average particle size of the Sn / Ge halide nanocrystals of the present invention is 10 to 150 nm, preferably 10 to 120 nm. In the present invention, the average particle size is determined by measuring the minor axis of 100 randomly selected particles in a TEM image obtained using a transmission electron microscope (TEM) (JEM-2100, manufactured by JEOL Ltd.) at an acceleration voltage of 200 kV, and averaging the obtained values.

[0031] The Sn / Ge halide nanocrystals of the present invention can be a solid powder.

[0032] In the Sn / Ge halide nanocrystals of the present invention, the molar ratio of the A site, the B site, and the X site in the general formula (1) is based on the form A:B:X=3:1:5. However, the Sn / Ge halide nanocrystals of the present invention may have a molar ratio of A:B:X that deviates from 3:1:5 as long as they can assume the structure shown in FIG. 1 .

[0033] The peak of the emission wavelength of the Sn / Ge halide nanocrystals of the present invention is 600 nm, preferably 620 nm or more.

[0034] The fluorescence quantum yield (PLQY) of the Sn / Ge halide nanocrystals of the present invention is 30% or more, preferably 50% or more, and more preferably 80% or more.

[0035] The Sn / Ge halide nanocrystal composite of the present invention comprises the Sn / Ge halide nanocrystal of the present invention (i.e., the Sn / Ge halide nanocrystal represented by general formula (1)), and a ligand bound to the Sn / Ge halide nanocrystal, wherein the ligand has a lipophilic molecular chain and / or a hydrophilic molecular chain and a binding group.

[0036] The Sn / Ge halide nanocrystal composite of the present invention has a ligand bonded to the Sn / Ge halide nanocrystal of the present invention. The ligand for the Sn / Ge halide nanocrystal composite of the present invention has a lipophilic molecular chain and / or a hydrophilic molecular chain and a binding group capable of bonding to the Sn / Ge halide nanocrystal composite. The ligand serves functions such as preventing aggregation of Sn / Ge halide nanocrystal particles, improving dispersibility in a dispersion medium, and preventing deterioration in weather resistance, water resistance, oxidation resistance, impact resistance, and the like. Furthermore, by having the ligand, the Sn / Ge halide nanocrystal composite of the present invention exhibits an emission wavelength peak at a longer wavelength in the red or near-infrared range than conventional Sn / Ge halide nanocrystal composites, specifically, an emission wavelength peak at a wavelength longer than 600 nm, thereby achieving a narrower emission band and a higher fluorescence quantum yield (PLQY).

[0037] The ligand of the Sn / Ge halide nanocrystal composite of the present invention has a lipophilic molecular chain and / or a hydrophilic molecular chain. Examples of the lipophilic molecular chain of the ligand include saturated hydrocarbon chains, hydrocarbon chains partially containing double bonds, and hydrocarbon chains containing aromatic groups. The length of the hydrocarbon chain of the lipophilic molecular chain of the ligand preferably has 3 or more carbon atoms, more preferably 3 to 30, and even more preferably 4 to 20. The molecular weight of the lipophilic molecular chain of the ligand is preferably 43.08 or more, more preferably 43.08 to 1265.4, and even more preferably 57.11 to 844.6. Examples of the hydrophilic molecular chain of the ligand include polyoxyalkylene chains such as polyoxyethylene chains and polyoxypropylene chains.

[0038] The ligand in the Sn / Ge halide nanocrystal composite of the present invention may have both the lipophilic organic chain and the hydrophilic organic chain.

[0039] The ligand in the Sn / Ge halide nanocrystal composite of the present invention has a binding group capable of binding to the Sn / Ge halide nanocrystal composite. The binding group possessed by the ligand is a quaternary ammonium group (—NH ４ ＋ ), carboxyl group (-COOH), phosphate group (H ２ P.O. ４ -), sulfonic acid group (-SO ３ In the Sn / Ge halide nanocrystal composite of the present invention, the binding group is bonded to the surface of the Sn / Ge halide nanocrystal of the present invention by a coordinate bond, an ionic bond, or a covalent bond, thereby bonding the ligand to the Sn / Ge halide nanocrystal of the present invention.

[0040] Examples of the ligands for the Sn / Ge halide nanocrystal composite of the present invention include ligands having a quaternary ammonium group such as an oleylammonium group, ligands having a carboxyl group such as oleic acid, and ligands having a phosphate group. Also, examples of the ligands include phosphines and phosphine oxides such as trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), and tributylphosphine (TOP). Examples of the ligand include phosphonic acids such as dodecylphosphonic acid (DDPA), tridecylphosphonic acid (TDPA), octadecylphosphonic acid (ODPA), and hexylphosphonic acid (HPA); amines such as dodecylamine (DDA), tetradecylamine (TDA), hexadecylamine (HDA), octadecylamine (ODA), oleylamine (OLA), and 1-octadecene (ODE); thiols such as hexadecanethiol and hexanethiol; mercaptocarboxylic acids such as mercaptopropionic acid and mercaptoundecanoic acid; carboxylic acids such as oleic acid, stearic acid, and myristic acid; acetic acid, polyethyleneimine (PEI), monofunctional PEG thiol (mPEG thiol), and derivatives of mPEG thiol. The above ligands may be used alone or in any combination of two or more.

[0041] The average particle size of the Sn / Ge halide nanocrystal composite of the present invention is 10 to 150 nm, preferably 10 to 120 nm. In the present invention, the average particle size is determined by measuring the minor axis of 100 randomly selected particles in a TEM image obtained using a transmission electron microscope (TEM) (JEM-2100, manufactured by JEOL Ltd.) at an acceleration voltage of 200 kV, and averaging the measured values.

[0042] The Sn / Ge halide nanocrystalline composite of the present invention can be a solid powder.

[0043] The Sn / Ge halide nanocrystal composite of the present invention has an emission wavelength peak of 600 nm or more, preferably 620 nm or more.

[0044] The Sn / Ge halide nanocrystal composite of the present invention has a fluorescence quantum yield (PLQY) of 30% or more, preferably 50% or more, and more preferably 80% or more.

[0045] The Sn / Ge halide nanocrystals and Sn / Ge halide nanocrystal composites of the present invention are nano-sized crystals with small average particle sizes, preferably 10 to 150 nm, more preferably 10 to 120 nm, making them useful for application in terms of dispersibility and other factors.

[0046] The Sn / Ge halide nanocrystals and the Sn / Ge halide nanocrystal composites of the present invention use Ge as an antioxidant for Sn, thereby preventing the oxidation of Sn involved in the phase transition. ４＋ Since the ratio of is reduced, the stability over time and the oxidation stability are improved.

[0047] The Sn / Ge halide nanocrystals of the present invention and the Sn / Ge halide nanocrystal composite of the present invention are preferably produced by the method for producing Sn / Ge halide nanocrystals of the present invention, which will be explained below.

[0048] The first embodiment of the method for producing the Sn / Ge halide nanocrystals of the present invention is to mix and react a solution obtained by mixing tin bromide and / or tin iodide, germanium bromide and / or germanium iodide in a solvent with a solution obtained by mixing a cesium precursor in a solvent, by a hot injection method, to form a compound represented by the following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), a nanocrystal synthesis step (A) is provided for obtaining Sn / Ge halide nanocrystals represented by the formula: (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), wherein, among all raw materials mixed in the nanocrystal synthesis step (A), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, and the molar ratio of Br to the total of Br and I (Br / (Br+I)) is 0.00 to 1.00, on an atomic basis.

[0049] The first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention is a method for directly synthesizing nanocrystals of the Sn / Ge halide compound represented by general formula (1).

[0050] The first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention includes a nanocrystal synthesis step (A) in which a solution obtained by mixing tin bromide and / or tin iodide with germanium bromide and / or germanium iodide in a solvent is mixed with a solution obtained by mixing a cesium precursor in a solvent and reacted with each other by a hot injection method to obtain Sn / Ge halide nanocrystals represented by the following general formula (1):

[0051] In the nanocrystal synthesis step (A) of the first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention, nanocrystals of a Sn / Ge halide compound represented by general formula (1) are obtained by a hot injection method. The hot injection method is a method in which a metal compound as a reaction raw material is rapidly added to a high-temperature solvent to uniformly form nuclei of nanocrystal particles.

[0052] In the nanocrystal synthesis step (A), tin bromide (SnBr ２ ), or tin iodide (SnI ２ ), or tin bromide (SnBr ２ ) and tin iodide (SnI ２ ) as a germanium source, and germanium bromide (GeBr ２ ), or germanium iodide (GeI ２ ), or germanium bromide (GeBr ２ ) and germanium iodide (GeI ２ Nanocrystals of the Sn / Ge halide compound represented by the general formula (1) are obtained by injecting a solution (1a) prepared by mixing a cesium precursor and a ligand compound such as oleic acid (OA), oleylamine (OAm), or trioctylphosphine (TOP) in a solvent such as 1-octadecene (ODE) and dissolving the cesium precursor and the ligand compound such as oleic acid (OA) in a solvent such as 1-octadecene (ODE) into the solution (2a) prepared by mixing the cesium precursor and the ligand compound such as oleic acid (OA) in a solvent such as 1-octadecene (ODE).

[0053] The cesium precursor used in the nanocrystal synthesis step (A) is a compound containing cesium, such as cesium oleate.

[0054] In the nanocrystal synthesis step (A), the ligand compound used to prepare solution (1a) and the ligand compound used to prepare solution (2a) have a lipophilic molecular chain and / or a hydrophilic molecular chain and a binding group capable of binding to the Sn / Ge halide nanocrystal composite, such as a quaternary ammonium group, a carboxyl group, a phosphate group, or a sulfonic acid group.

[0055] The ligand compound used in the nanocrystal synthesis step (A) has a lipophilic molecular chain and / or a hydrophilic molecular chain. Examples of the lipophilic molecular chain of the ligand compound include saturated hydrocarbon chains, hydrocarbon chains partially containing double bonds, and hydrocarbon chains containing aromatic groups. The length of the hydrocarbon chain of the lipophilic molecular chain of the ligand compound preferably has 3 or more carbon atoms, more preferably 3 to 30, and even more preferably 4 to 20. The molecular weight of the lipophilic molecular chain of the ligand compound is preferably 43.08 or more, more preferably 43.08 to 1265.4, and even more preferably 57.11 to 844.6. Examples of the hydrophilic molecular chain of the ligand compound include polyoxyalkylene chains such as polyoxyethylene chains and polyoxypropylene chains.

[0056] The ligand compound used in the nanocrystal synthesis step (A) may have both the lipophilic organic chain and the hydrophilic organic chain.

[0057] The ligand compound used in the nanocrystal synthesis step (A) has a binding group capable of binding to the Sn / Ge halide nanocrystal composite. The binding group of the ligand compound is a quaternary ammonium group (—NH ４ ＋ ), carboxyl group (-COOH), phosphate group (H ２ P.O. ４ -) or sulfonic acid group (-SO ３ H).

[0058] In the nanocrystal synthesis step (A), examples of the ligand compound used in preparing the solution (1a) include oleic acid, oleylamine, etc. In addition, examples of the ligand compound include phosphines and phosphine oxides such as trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), and tributylphosphine (TOP). Examples of the ligand compound include phosphonic acids such as dodecylphosphonic acid (DDPA), tridecylphosphonic acid (TDPA), octadecylphosphonic acid (ODPA), and hexylphosphonic acid (HPA); amines such as dodecylamine (DDA), tetradecylamine (TDA), hexadecylamine (HDA), octadecylamine (ODA), oleylamine (OLA), and 1-octadecene (ODE); thiols such as hexadecanethiol and hexanethiol; mercaptocarboxylic acids such as mercaptopropionic acid and mercaptoundecanoic acid; carboxylic acids such as oleic acid, stearic acid, and myristic acid; acetic acid, polyethyleneimine (PEI), monofunctional PEG thiol (mPEG thiol), and derivatives of mPEG thiol. The ligand compounds may be used alone or in any combination of two or more. For example, by using trioctylphosphine (TOP) as a ligand compound, germanium iodide, which is poorly soluble, can be dissolved to prepare solution (1a).

[0059] In the nanocrystal synthesis step (A), examples of the ligand compound used in preparing the solution (2a) include oleic acid, oleylamine, etc. In addition, examples of the ligand compound include phosphines and phosphine oxides such as trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), and tributylphosphine (TOP). Examples of the ligand compound include phosphonic acids such as dodecylphosphonic acid (DDPA), tridecylphosphonic acid (TDPA), octadecylphosphonic acid (ODPA), and hexylphosphonic acid (HPA); amines such as dodecylamine (DDA), tetradecylamine (TDA), hexadecylamine (HDA), octadecylamine (ODA), oleylamine (OLA), and 1-octadecene (ODE); thiols such as hexadecanethiol and hexanethiol; mercaptocarboxylic acids such as mercaptopropionic acid and mercaptoundecanoic acid; carboxylic acids such as oleic acid, stearic acid, and myristic acid; acetic acid, polyethyleneimine (PEI), monofunctional PEG thiol (mPEG thiol), and derivatives of mPEG thiol. The ligand compounds may be used alone or in any combination of two or more.

[0060] In the nanocrystal synthesis step (A), the solvent used to prepare the solution (1a) and the solvent (2a) is a high-boiling solvent, and is preferably selected from aromatic solvents such as 1-octadecene, squalene, squalane, heptadecane, octadecane, octadecene, nonadecane, icosane, henicosane, docosane, tricosane, pentacosane, hexacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, oleylamine, trioctylamine, ketones, ketone ether acetates such as propylene glycol methyl ether acetate (PGMEA), nitriles, ethers, ether esters, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, diisopropylbenzene, and methylene. Particularly preferred solvents include squalene, squalane, heptadecane, octadecane, octadecene, nonadecane, icosane, henicosane, docosane, tricosane, pentacosane, hexacosane, octacosane, tetracosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, oleylamine, trioctylamine, ketones, ketone ether acetates such as PGMEA, nitriles, ethers, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, diisopropylbenzene, and meditylene. Furthermore, the solvent is more preferably octadecene, oleylamine, squalane, pentacosane, hexacosane, octacosane, nonacosane, trioctylamine or triacontane, ketone, ketone ether acetate (including PGMEA), nitrile, ether, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, diisopropylbenzene, or methylenediamine.Further, the solvent is more preferably octadecene, oleylamine, squalane, pentacosane, trioctylamine or hexacosane, tetracosane, ketone, ketone ether acetate (including PGMEA), ether ester, nitrile, ether, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, diisopropylbenzene, or methylene.

[0061] The solution (1a) for the nanocrystal synthesis step (A) is tin bromide (SnBr ２ ) and / or tin iodide (SnI ２ ) and germanium bromide (GeBr ２ ) and / or germanium iodide (GeI ２ The mixture is prepared by mixing the above-mentioned compound (I) and the ligand compound in a solvent and heating the mixture to 100 to 140° C., preferably 110 to 130° C. The heating time is preferably 30 to 120 minutes.

[0062] The solution (2a) for the nanocrystal synthesis step (A) is prepared by mixing a cesium precursor and a ligand in a solvent and heating the mixture to 150 to 300° C., preferably 220 to 280° C. The heating time is preferably 5 to 300 seconds.

[0063] In all raw materials mixed in the nanocrystal synthesis step (A), the ratio of the number of moles of Sn to the total number of moles of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, preferably greater than 0.00 and 0.40 or less, more preferably 0.05 to 0.35, more preferably 0.10 to 0.30. In addition, in all raw materials mixed in the nanocrystal synthesis step (A), the ratio of the number of moles of Br to the total number of moles of Br and I (Br / (Br+I)) is 0.00 to 1.00, preferably greater than 0.00 and less than 1.00, more preferably 0.05 to 0.95, more preferably 0.10 to 0.90, more preferably 0.20 to 0.80, more preferably 0.30 to 0.70. By keeping the (Sn / (Sn+Ge)) ratio and (Br / (Br+I)) ratio within the above ranges, the peak emission wavelength of the Sn / Ge halide nanocrystals can be shifted to a longer wavelength. Note that the (Sn / (Sn+Ge)) ratio and (Br / (Br+I)) ratio are adjusted by the amounts of tin iodide, germanium bromide, tin bromide, and germanium iodide mixed in the nanocrystal synthesis step (A).

[0064] In all raw materials mixed in the nanocrystal synthesis step (A), the ratio of the number of moles of Cs to the total number of moles of Sn and Ge (Cs / (Sn+Ge)) is 2.0 to 4.0, preferably 2.5 to 3.5, in atomic terms.

[0065] In the nanocrystal synthesis step (A), solution (1a) serving as a Sn source, Ge source, Br source, and I source and solution (2a) serving as a Cs source are rapidly mixed and reacted in a high-temperature solvent, resulting in uniform nucleation of nanocrystalline particles. This results in nano-sized crystal particles with small and uniform particle sizes. The reaction temperature during the mixing and reaction of solution (1a) and solution (2a) is preferably 150 to 300°C, more preferably 220 to 280°C. The time from the start of mixing solution (1a) and solution (2a) to the completion of mixing the entire amount is preferably 5 to 300 seconds, more preferably 10 to 120 seconds.

[0066] In the nanocrystal synthesis step (A), solutions (1a) and (2a) are mixed and reacted, and then the reaction solution is rapidly cooled. After cooling, the solid powder of Sn / Ge halide nanocrystals represented by general formula (1) can be recovered without aggregation by reprecipitation washing with a poor solvent and drying under reduced pressure.

[0067] The Sn / Ge halide nanocrystals obtained by carrying out the nanocrystal synthesis step (A) are bound to the ligands used in preparing the solutions (1a) and (2a). In other words, by carrying out the nanocrystal synthesis step (A), the Sn / Ge halide nanocrystals of the present invention and the Sn / Ge halide nanocrystal composite of the present invention are obtained.

[0068] The second embodiment of the method for producing the Sn / Ge halide nanocrystals of the present invention is a hot injection method in which a solution obtained by mixing tin bromide and germanium bromide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted with each other to form a compound represented by the following general formula (2): Cs ３ (Sn α２ Ge （１－α２） )Br ５ (2) (wherein α2 is 0.00 to 0.40), a nanocrystal synthesis step (B) of obtaining Sn / Ge halide nanocrystals represented by the general formula (2) and a salt of a metal cation or an organic cation and an iodine anion, and a halogen substitution reaction is carried out to obtain a Sn / Ge halide nanocrystal represented by the general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５(1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (C) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in all raw materials mixed in the nanocrystal synthesis step (B), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, on an atomic basis; and in the halogen substitution step (C), the ratio (I / Br) of the number of moles of I in atom terms in a salt of a metal cation or an organic cation and an iodine anion to the number of moles in atom terms of Br in the Sn / Ge halide nanocrystals represented by the formula (2) is 0.00 to 5.00.

[0069] The second embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention comprises a nanocrystal synthesis step (B) and a halogen substitution step (C). In other words, after synthesizing Sn / Ge halide nanocrystals represented by general formula (2), halogen substitution is carried out by an anion substitution reaction through post-treatment, thereby synthesizing Sn / Ge halide nanocrystals represented by general formula (1).

[0070] The nanocrystal synthesis step (B) according to the second method for producing Sn / Ge halide nanocrystals of the present invention is a hot injection method in which a solution obtained by mixing tin bromide and germanium bromide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted to form a compound represented by the following general formula (2): Cs ３ (Sn α２ Ge （１－α２） )Br ５ (2) (wherein α2 is 0.00 to 0.40), α2 is 0.00 to 0.40, preferably greater than 0.00 and not greater than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30.

[0071] In the nanocrystal synthesis step (B), Sn / Ge halide nanocrystals represented by the general formula (2) are obtained by the hot injection method.

[0072] In the nanocrystal synthesis step (B), tin bromide (SnBr２ ) and germanium bromide (GeBr ２ Nanocrystals of the Sn / Ge halide compound represented by the general formula (2) are obtained by injecting a solution (1b) prepared by mixing a cesium precursor and a ligand compound such as oleic acid (OA) or oleylamine (OAm) in a solvent such as 1-octadecene (ODE) and dissolving the mixture into the solution (1b). The nanocrystals are obtained by injecting a solution (2b) prepared by mixing a cesium precursor and a ligand compound such as oleic acid (OA) in a solvent such as 1-octadecene (ODE).

[0073] The cesium precursor, ligand compound, and solvent used in the nanocrystal synthesis step (B) are the same as the cesium precursor, ligand compound, and solvent used in the nanocrystal synthesis step (A) in the first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention.

[0074] The solution (1b) for the nanocrystal synthesis step (B) is tin bromide (SnBr ２ ) and germanium bromide (GeBr ２ The mixture is prepared by mixing the above-mentioned compound (I) and the ligand compound in a solvent and heating the mixture to 100 to 140° C., preferably 110 to 130° C. The heating time is preferably 30 to 120 minutes.

[0075] The solution (2b) for the nanocrystal synthesis step (B) is prepared by mixing the cesium precursor and the ligand in a solvent and heating the mixture to 150 to 300° C., preferably 220 to 280° C. The heating time is preferably 5 to 300 seconds.

[0076] In the nanocrystal synthesis step (B), the ratio of the number of moles of Sn to the total number of moles of Sn and Ge, in atomic terms (Sn / (Sn+Ge)), is 0.00 to 0.40, preferably greater than 0.00 and not greater than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. By having the (Sn / (Sn+Ge)) ratio in the above range, the peak emission wavelength of the Sn / Ge halide nanocrystals can be shifted to a longer wavelength.

[0077] In all raw materials mixed in the nanocrystal synthesis step (B), the ratio of the number of moles of Cs to the total number of moles of Sn and Ge (Cs / (Sn+Ge)) is 2.0 to 4.0, preferably 2.5 to 3.5, in atomic terms.

[0078] In the nanocrystal synthesis step (B), solution (1b) serving as a Sn source, Ge source, and Br source and solution (2b) serving as a Cs source are rapidly mixed and reacted in a high-temperature solvent, thereby uniformly nucleating nanocrystal particles. The reaction temperature during the mixing and reaction of solution (1b) and solution (2b) is preferably 150 to 300°C, more preferably 220 to 280°C. The time from the start of mixing solution (1b) and solution (2b) to the completion of mixing the entire amount is preferably 5 to 300 seconds, more preferably 10 to 120 seconds.

[0079] In the nanocrystal synthesis step (B), solutions (1b) and (2b) are mixed and reacted, and the reaction solution is then rapidly cooled. After cooling, the solid powder of Sn / Ge halide nanocrystals represented by general formula (2) can be recovered without aggregation by reprecipitation washing with a poor solvent and drying under reduced pressure.

[0080] The halogen substitution step (C) is a step of mixing the Sn / Ge halide nanocrystals represented by the general formula (2) obtained in the nanocrystal synthesis step (B) with a salt of a metal cation or an organic cation and an iodine anion, and then performing a halogen substitution reaction to form a compound represented by the following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), this is a process for obtaining Sn / Ge halide nanocrystals represented by the formula: α1 is 0.00 to 0.40, preferably greater than 0.00 and equal to or less than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. β1 is 0.00 to 1.00, preferably greater than 0.00 and less than 1.00, and more preferably 0.05 to 0.30.

[0081] In the halogen substitution step (C), a portion of the Br element in the X site of the Sn / Ge halide nanocrystal represented by general formula (2) obtained in the nanocrystal synthesis step (B) is substituted with the I element of a salt of a metal cation or an organic cation and an iodine anion, thereby obtaining a Sn / Ge halide nanocrystal represented by general formula (1).

[0082] Examples of the salts of metal cations or organic cations and iodine anions used in the halogen substitution step (C) include salts of a ligand having a lipophilic molecular chain and / or a hydrophilic molecular chain and a cationic binding group such as a quaternary ammonium group, i.e., a cationic ligand and an iodine ion. In other words, examples of the salts of organic cations and iodine anions include iodide salts of cationic ligands, which are salts in which the anion is an iodine ion and the counter cation is a cationic ligand. The cationic ligand is composed of a lipophilic molecular chain and / or a hydrophilic molecular chain and has a cationic binding group.

[0083] The cationic ligand of the iodide salt of the cationic ligand has a lipophilic molecular chain and / or a hydrophilic molecular chain. Examples of the lipophilic molecular chain of the cationic ligand include saturated hydrocarbon chains, hydrocarbon chains partially containing double bonds, and hydrocarbon chains containing aromatic groups. The length of the hydrocarbon chain of the lipophilic molecular chain of the cationic ligand preferably has 3 or more carbon atoms, more preferably 3 to 30, and even more preferably 4 to 20 carbon atoms. The molecular weight of the lipophilic molecular chain of the ligand is preferably 43.08 or more, more preferably 43.08 to 1265.4, and more preferably 57.11 to 844.6. Examples of the hydrophilic molecular chain of the cationic ligand include polyoxyalkylene chains such as polyoxyethylene chains and polyoxypropylene chains.

[0084] The cationic ligand in the iodide salt of the cationic ligand may have both the lipophilic organic chain and the hydrophilic organic chain.

[0085] The cationic ligand in the iodide salt of the cationic ligand is a quaternary ammonium group (—NH ４ ＋ , -NH３ R ＋ , -NH ２ R ２ ＋ , -NHR ３ ＋ , -NR ４ ＋ R is an alkyl group, an alkenyl group, or an aromatic group, and when there are a plurality of Rs, they may be the same or different.

[0086] Examples of the cationic ligand relating to the iodide salt of a cationic ligand include quaternary ammonium groups such as oleylammonium, dodecylammonium, tetrabutylammonium, trimethylphenylammonium, and tetraphenylammonium.

[0087] Examples of iodide salts of cationic ligands include iodide salts of cationic ligands having a quaternary ammonium group, such as oleylammonium iodide (OAmI), dodecylammonium iodide (DDAI), tetrabutylammonium iodide (TBAI), aniline hydroiodide, and tetraphenylammonium iodide.

[0088] The salt of a metal cation or organic cation and an iodine anion used in the halogen substitution step (C) may be a salt of a metal cation and an iodine anion. In the present invention, a salt of a metal cation and an iodine anion, i.e., an iodide salt of a metal cation, may be used as long as it does not destroy the crystal structure of the Sn / Ge halide nanocrystals represented by general formula (2) obtained in the nanocrystal synthesis step (B).

[0089] In the halogen substitution step (C), the ratio of the moles of I in atomic terms in the salt of a metal cation or organic cation and an iodine anion to the moles of Br in atomic terms in the Sn / Ge halide nanocrystal represented by general formula (2) (I / Br) is 0.00 to 5.00, preferably 0.00 to 1.00, more preferably greater than 0.00 and not greater than 1.00, and more preferably 0.05 to 0.30. By having the (I / Br) ratio in the above range, the peak emission wavelength of the Sn / Ge halide nanocrystal can be shifted to a longer wavelength.

[0090] In the halogen substitution step (C), the Sn / Ge halide nanocrystals represented by general formula (2) obtained in the nanocrystal synthesis step (B) and a salt of a metal cation or an organic cation and an iodine anion are added to an organic solvent such as toluene and mixed by stirring to react. The reaction temperature during the mixing and reaction of the Sn / Ge halide nanocrystals represented by general formula (2) with a salt of a metal cation or an organic cation and an iodine anion is preferably 60°C or lower. The reaction time between the Sn / Ge halide nanocrystals represented by general formula (2) and a salt of a metal cation or an organic cation and an iodine anion is 5 to 120 minutes.

[0091] After the halogen substitution step (C), a solid powder of Sn / Ge halide nanocrystals represented by general formula (1) can be recovered without aggregation by reprecipitation washing using a poor solvent and drying under reduced pressure.

[0092] The Sn / Ge halide nanocrystals obtained by carrying out the halogen substitution step (C) are bound to the ligands used in preparing solutions (1b) and (2b) and the cationic ligands derived from the salts of metal cations or organic cations and iodine anions used in the halogen substitution step (C). In other words, by carrying out the halogen substitution step (C), the Sn / Ge halide nanocrystals of the present invention and the Sn / Ge halide nanocrystal composite of the present invention are obtained.

[0093] The third embodiment of the present invention is a method for producing Sn / Ge halide nanocrystals by a hot injection method in which a solution obtained by mixing tin iodide and germanium iodide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted with each other, the method comprising: ３ (Sn α３ Ge （１－α３） ) I ５ (3) (wherein α3 is 0.00 to 0.40), a nanocrystal synthesis step (D) of obtaining Sn / Ge halide nanocrystals represented by the general formula (3) and a salt of a metal cation or an organic cation and a bromine anion, and by a halogen substitution reaction, obtaining Sn / Ge halide nanocrystals represented by the general formula (1): Cs３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (E) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in the nanocrystal synthesis step (D), the molar ratio of Sn to the total of Sn and Ge, on an atomic basis (Sn / (Sn+Ge)), is 0.00 to 0.40; and in the halogen substitution step (E), the ratio (Br / I) of the number of moles of Br, on an atomic basis, in a salt of a metal cation or an organic cation and a bromine anion to the number of moles of I, on an atomic basis, in the Sn / Ge halide nanocrystals represented by the formula (2), is 0.00 to 5.00.

[0094] The third embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention comprises a nanocrystal synthesis step (D) and a halogen substitution step (E). In other words, after synthesizing Sn / Ge halide nanocrystals represented by general formula (3), halogen substitution is carried out by an anion substitution reaction through post-treatment, thereby synthesizing Sn / Ge halide nanocrystals represented by general formula (1).

[0095] The nanocrystal synthesis step (D) according to the third method for producing Sn / Ge halide nanocrystals of the present invention is a hot injection method in which a solution obtained by mixing tin iodide and germanium iodide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted with each other to form a compound represented by the following general formula (3): Cs ３ (Sn α３ Ge （１－α３） ) I ５ (3) (wherein α3 is 0.00 to 0.40), α3 is 0.00 to 0.40, preferably greater than 0.00 and not greater than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30.

[0096] In the nanocrystal synthesis step (D), Sn / Ge halide nanocrystals represented by the general formula (3) are obtained by the hot injection method.

[0097] In the nanocrystal synthesis step (D), tin iodide (SnI ２ ) and germanium iodide (GeI ２ Nanocrystals of a Sn / Ge halide compound represented by general formula (3) are obtained by a hot injection method in which a cesium precursor and a ligand compound such as oleic acid (OA), oleylamine (OAm), or trioctylphosphine (TOP) are mixed in a solvent such as 1-octadecene (ODE) to form a solution (1c), and then a solution (2c) is formed by mixing a cesium precursor and a ligand compound such as oleic acid (OA) in a solvent such as 1-octadecene (ODE) and dissolving the mixture. In the nanocrystal synthesis step (D), for example, trioctylphosphine (TOP) is used as the ligand compound, which allows germanium iodide, which has poor solubility, to be dissolved to form solution (1c).

[0098] The cesium precursor, ligand compound, and solvent used in the nanocrystal synthesis step (D) are the same as the cesium precursor, ligand compound, and solvent used in the nanocrystal synthesis step (A) in the first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention.

[0099] The solution (1c) for the nanocrystal synthesis step (D) contains tin iodide (SnI ２ ) and germanium iodide (GeI ２ The mixture is prepared by mixing the above-mentioned compound (I) and the ligand compound in a solvent and heating the mixture to 100 to 140° C., preferably 110 to 130° C. The heating time is preferably 30 to 120 minutes.

[0100] The solution (2c) involved in the nanocrystal synthesis step (D) is prepared by mixing the cesium precursor and the ligand in a solvent and heating the mixture to 150 to 300° C., preferably 220 to 280° C. The heating time is preferably 5 to 300 seconds.

[0101] In the nanocrystal synthesis step (D), the ratio of the number of moles of Sn to the total number of moles of Sn and Ge, in atomic terms (Sn / (Sn+Ge)), is 0.00 to 0.40, preferably greater than 0.00 and not greater than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. By having the (Sn / (Sn+Ge)) ratio in the above range, the peak emission wavelength of the Sn / Ge halide nanocrystals can be shifted to a longer wavelength.

[0102] In all the raw materials mixed in the nanocrystal synthesis step (D), the ratio of the number of moles of Cs to the total number of moles of Sn and Ge, in atomic terms, is 2.0 to 4.0, preferably 2.5 to 3.5.

[0103] In the nanocrystal synthesis step (D), solution (1c) serving as a Sn source, Ge source, and I source and solution (2c) serving as a Cs source are rapidly mixed and reacted in a high-temperature solvent, thereby uniformly nucleating nanocrystal particles. The reaction temperature during the mixing and reaction of solution (1c) and solution (2c) is preferably 150 to 300°C, more preferably 220 to 280°C. The time from the start of mixing solution (1c) and solution (2c) to the completion of mixing the entire amount is preferably 5 to 300 seconds, more preferably 10 to 120 seconds.

[0104] In the nanocrystal synthesis step (D), solutions (1c) and (2c) are mixed and reacted, and the reaction solution is then rapidly cooled. After cooling, the solid powder of Sn / Ge halide nanocrystals represented by general formula (3) can be recovered without aggregation by reprecipitation washing with a poor solvent and drying under reduced pressure.

[0105] The halogen substitution step (E) is a step of mixing the Sn / Ge halide nanocrystals represented by the general formula (3) obtained in the nanocrystal synthesis step (D) with a salt of a metal cation or an organic cation and a bromine anion, and then converting the Sn / Ge halide nanocrystals into the Sn / Ge halide nanocrystals represented by the general formula (3) by a halogen substitution reaction. ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５(1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), this is a process for obtaining Sn / Ge halide nanocrystals represented by the formula: α1 is 0.00 to 0.40, preferably greater than 0.00 and equal to or less than 0.40, more preferably 0.05 to 0.35, and more preferably 0.10 to 0.30. β1 is 0.00 to 1.00, preferably greater than 0.00 and less than 1.00, and more preferably 0.05 to 0.30.

[0106] In the halogen substitution step (E), a portion of the I element at the X site of the Sn / Ge halide nanocrystal represented by general formula (3) obtained in the nanocrystal synthesis step (D) is substituted with the Br element of a salt of a metal cation or an organic cation and a bromine anion, thereby obtaining a Sn / Ge halide nanocrystal represented by general formula (1).

[0107] Examples of the salts of metal cations or organic cations and bromine anions used in the halogen substitution step (E) include salts of a ligand having a lipophilic molecular chain and / or a hydrophilic molecular chain and a cationic binding group such as a quaternary ammonium group, i.e., a cationic ligand and a bromide ion. That is, examples of the salts of metal cations or organic cations and bromine anions include bromide salts of cationic ligands, which are salts in which the anion is a bromide ion and the counter cation is a cationic ligand. The cationic ligand is composed of a lipophilic molecular chain and / or a hydrophilic molecular chain and has a cationic binding group.

[0108] The cationic ligand of the bromide salt of the cationic ligand has a lipophilic molecular chain and / or a hydrophilic molecular chain. Examples of the lipophilic molecular chain of the cationic ligand include saturated hydrocarbon chains, hydrocarbon chains partially containing double bonds, and hydrocarbon chains containing aromatic groups. The length of the hydrocarbon chain of the lipophilic molecular chain of the cationic ligand preferably has 3 or more carbon atoms, more preferably 3 to 30, and even more preferably 4 to 20 carbon atoms. The molecular weight of the lipophilic molecular chain of the ligand is preferably 43.08 or more, more preferably 43.08 to 1265.4, and more preferably 57.11 to 844.6. Examples of the hydrophilic molecular chain of the cationic ligand include polyoxyalkylene chains such as polyoxyethylene chains and polyoxypropylene chains.

[0109] The cationic ligand in the bromide salt of the cationic ligand may have both the lipophilic organic chain and the hydrophilic organic chain.

[0110] The cationic ligand in the bromide salt of the cationic ligand is a quaternary ammonium group (—NH ４ ＋ , -NH ３ R ＋ , -NH ２ R ２ ＋ , -NHR ３ ＋ , -NR ４ ＋ R is an alkyl group, an alkenyl group, or an aromatic group, and when there are a plurality of Rs, they may be the same or different.

[0111] Examples of the cationic ligand relating to the bromide salt of a cationic ligand include quaternary ammonium groups such as oleylammonium, dodecylammonium, tetrabutylammonium, trimethylphenylammonium, and tetraphenylammonium.

[0112] Examples of bromide salts of cationic ligands include bromide salts of cationic ligands having a quaternary ammonium group, such as oleylammonium bromide (OAmBr), dodecylammonium bromide (DDABr), tetrabutylammonium bromide (TBABr), aniline hydrobromide, and tetraphenylammonium bromide.

[0113] The salt of a metal cation or organic cation and a bromine anion used in the halogen substitution step (E) may be a salt of a metal cation and a bromine anion. In the present invention, a salt of a metal cation and a bromine anion, i.e., a bromide salt of a metal cation, may be used as long as it does not destroy the crystal structure of the Sn / Ge halide nanocrystals represented by general formula (2) obtained in the nanocrystal synthesis step (B).

[0114] In the halogen substitution step (E), the ratio of the number of moles of Br in atomic terms in the salt of a metal cation or an organic cation and a bromine anion to the number of moles of I in atomic terms in the Sn / Ge halide nanocrystal represented by general formula (3) (Br / I) is 0.00 to 5.00, preferably 0.00 to 1.00, more preferably greater than 0.00 and not greater than 1.00, and more preferably 0.05 to 0.30. By having the (Br / I) ratio in the above range, the peak emission wavelength of the Sn / Ge halide nanocrystal can be shifted to a longer wavelength.

[0115] In the halogen substitution step (E), the Sn / Ge halide nanocrystals represented by general formula (3) obtained in the nanocrystal synthesis step (D) and a salt of a metal cation or an organic cation and a bromine anion are added to an organic solvent such as toluene and mixed by stirring to react. The reaction temperature during the mixing and reaction of the Sn / Ge halide nanocrystals represented by general formula (3) with a salt of a metal cation or an organic cation and a bromine anion is preferably 60°C or lower. The reaction time between the Sn / Ge halide nanocrystals represented by general formula (3) and a salt of a metal cation or an organic cation and a bromine anion is 5 to 120 minutes.

[0116] After the halogen substitution step (E), a solid powder of Sn / Ge halide nanocrystals represented by general formula (1) can be recovered without aggregation by reprecipitation washing using a poor solvent and drying under reduced pressure.

[0117] The Sn / Ge halide nanocrystals obtained by carrying out the halogen substitution step (E) are bound to the ligands used in preparing solutions (1c) and (2c) and the cationic ligands derived from the salts of metal cations or organic cations and bromine anions used in the halogen substitution step (E). In other words, by carrying out the halogen substitution step (E), the Sn / Ge halide nanocrystals of the present invention and the Sn / Ge halide nanocrystal composite of the present invention are obtained.

[0118] After carrying out the nanocrystal synthesis step (A) of the first embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention, a ligand exchange step may be carried out to exchange the ligands of the Sn / Ge halide nanocrystals represented by general formula (1) obtained by carrying out the nanocrystal synthesis step (A). Furthermore, after carrying out the halogen substitution step (C) of the second embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention or the halogen substitution step (E) of the third embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention, a ligand exchange step may be carried out to exchange the ligands of the Sn / Ge halide nanocrystals represented by general formula (1) obtained by carrying out the halogen substitution step (C) or the halogen substitution step (E). For example, if the ligand of the Sn / Ge halide nanocrystals represented by general formula (1) obtained by carrying out the first, second, or third embodiment of the method for producing Sn / Ge halide nanocrystals of the present invention is a highly lipophilic ligand, the dispersibility of the Sn / Ge halide nanocrystals of the present invention in aqueous solvents or polar organic solvents such as alcohols can be improved by ligand exchange with a more hydrophilic ligand.

[0119] The phosphor of the present invention is a phosphor characterized by comprising the Sn / Ge halide nanocrystal of the present invention.

[0120] The average particle size of the phosphor of the present invention is preferably 10 to 150 nm, more preferably 10 to 100 nm.

[0121] The fluorescent material of the present invention is a fluorescent material characterized by containing the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention. That is, the fluorescent material of the present invention consists of the Sn / Ge halide nanocrystals of the present invention, or the Sn / Ge halide nanocrystal composite of the present invention, or in addition to these, contains other components as necessary.

[0122] The fluorescent material of the present invention includes a fluorescent material characterized in that the surface of the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention is coated with a light-transmitting resin. That is, the fluorescent material of the present invention includes a fluorescent material containing the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention and a light-transmitting resin coating the surface of the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention.

[0123] The light-transmitting resin has a haze (JIS-K-7136) of 10% or less and a total light transmittance (JIS-K-7361) of 80% or more.

[0124] Examples of light-transmitting resins include polyethylene resin, polyvinyl chloride resin, acrylic resin, polycarbonate resin, polystyrene resin, polyamide resin, polypropylene resin, polyolefin resin, silicone resin, polyethylene terephthalate resin (PET resin), polybutylene terephthalate resin (PBT resin), polytetramethylene terephthalate resin (PTT), and the like.

[0125] When the fluorescent material of the present invention comprises the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention and a light-transmitting resin that coats the surface of the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention, if the coating material of the light-transmitting resin is too thin, the coating performance is not exhibited, and if it is too thick, the transparency is impaired, so the thickness of the light-transmitting resin is preferably 0.1 nm to 10 μm, and more preferably 1 nm to 5 μm.

[0126] Since the fluorescent material of the present invention is a fluorescent material comprising the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention and a light-transmitting resin coating the surface of the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention, when a resin sheet in which the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention is dispersed is produced, the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention are easily dispersed in the resin, making it easier to obtain a resin sheet in which the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention are uniformly dispersed.

[0127] In the fluorescent material of the present invention, the method for coating the surface of the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention with a light-transmitting resin is not particularly limited, and examples thereof include a method in which the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention are dispersed in a solvent, a monomer of a light-transmitting resin is added thereto, a polymerization initiator is then added, and the monomer of the light-transmitting resin is polymerized by heating or the like to produce a light-transmitting resin on the surface of the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention, thereby coating the surface of the Sn / Ge halide nanocrystals of the present invention or the Sn / Ge halide nanocrystal composite of the present invention with a light-transmitting resin.

[0128] The fluorescent material of the present invention can contain a spreading agent. The spreading agent enhances the wettability, adhesion, spreadability, suspension, etc. of the phosphor of the present invention or the fluorescent material of the present invention, thereby enabling the phosphor of the present invention or the fluorescent material of the present invention to be uniformly adhered. In particular, when the phosphor of the present invention or the fluorescent material of the present invention is used as an agricultural plant growth-promoting material by directly spraying the phosphor of the present invention or the fluorescent material of the present invention on plants to allow it to adhere directly to the leaves, stems, etc. of plants, the phosphor of the present invention or the fluorescent material of the present invention is adhered to the plants by spraying a dispersion of the phosphor of the present invention or the fluorescent material of the present invention in an aqueous solvent on the plants. The spreading agent is used to ensure that the phosphor of the present invention or the fluorescent material of the present invention is uniformly adhered to the surface of the plants at an appropriate density when the dispersion containing the phosphor of the present invention or the fluorescent material of the present invention is sprayed on the plants.

[0129] The spreading agent is not particularly limited as long as it can be used for agricultural purposes, and examples thereof include nonionic surfactants such as polyoxyethylene alkylphenyl ether surfactants, polyoxyethylene alkyl ether surfactants, polyalkylene glycol alkyl ether surfactants, polyoxyethylene fatty acid ester surfactants, polyoxyethylene resin acid ester surfactants, polyoxyethylene hexitane fatty acid ester surfactants, sorbitan fatty acid ester surfactants, and silicone surfactants as active ingredients; anionic surfactants such as naphthylmethanesulfonate surfactants, ligninsulfonate surfactants, and alkylsulfosuccinate surfactants as active ingredients; and cationic surfactants such as tetraalkylammonium salt surfactants. Commercially available spreading agents include Approach BI (registered trademark, manufactured by Maruwa Biochemical Co., Ltd.), Squash (registered trademark, manufactured by Maruwa Biochemical Co., Ltd.), Surfactant WK (registered trademark, manufactured by Maruwa Biochemical Co., Ltd.), Mixpower (registered trademark, manufactured by Syngenta Japan K.K.), and Supply (registered trademark, manufactured by OAT Agrio Co., Ltd.).

[0130] The content of the spreading agent in the fluorescent material of the present invention may be appropriately selected, but is, for example, 0.05 to 10% by mass, preferably 0.1 to 1.0% by mass, based on the phosphor.

[0131] The fluorescent material of the present invention is a fluorescent material comprising the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention, and a light-transmitting resin that coats the surface of the Sn / Ge halide nanocrystal of the present invention or the Sn / Ge halide nanocrystal composite of the present invention.When the fluorescent material is used by being dispersed in an aqueous dispersion solvent such as water, alcohol, or a mixed solvent thereof, or an lipophilic dispersion solvent such as aromatic hydrocarbons such as toluene, xylene, and benzene, aliphatic hydrocarbons such as pentane and hexane, ethers such as dioxane and dibutyl ether, and esters such as ethyl acetate, the fluorescent material of the present invention and a spreading agent can be mixed into the dispersion solvent and used.

[0132] The phosphor of the present invention can be dispersed in an aqueous dispersion solvent such as water, alcohol, or a mixture thereof, or in a lipophilic dispersion solvent such as aromatic hydrocarbons such as toluene, xylene, and benzene, aliphatic hydrocarbons such as pentane and hexane, ethers such as dioxane and dibutyl ether, and esters such as ethyl acetate. In this case, the phosphor of the present invention and a spreading agent can be mixed into the dispersion solvent and used.

[0133] When the phosphor or fluorescent material of the present invention is used as an agricultural plant growth material, a method of using the phosphor or fluorescent material of the present invention may include, for example, dispersing the phosphor or fluorescent material of the present invention in an aqueous solvent and spraying the resulting dispersion directly onto plants to adhere the phosphor of the present invention to the surfaces of the leaves, stems, etc. of the plants.

[0134] The use of the phosphor or fluorescent material of the present invention may be any use that requires emission in the visible to infrared light region, and may be any use that requires conversion of light of preferably 300 to 600 nm, preferably 300 to 550 nm, to light of 650 to 900 nm, preferably 650 to 750 nm, and emission of the converted light. Examples of uses of the phosphor or fluorescent material of the present invention include phosphors for white LEDs, ultraviolet absorbers, phosphors for wavelength conversion films for silicon solar cells, wavelength conversion materials for agricultural sheets for plant growth control, security fields, biosensors, and the like.

[0135] The resin sheet of the present invention is a resin sheet comprising a light-transmitting resin substrate and containing the phosphor of the present invention or the fluorescent material of the present invention.

[0136] The resin sheet of the present invention is made of a light-transmitting resin substrate. That is, the resin sheet of the present invention is a sheet-shaped product of a light-transmitting resin. Examples of the light-transmitting resin used in the resin sheet of the present invention include the same light-transmitting resins as those used in the fluorescent material of the present invention.

[0137] The content of the phosphor of the present invention or the fluorescent material of the present invention in the resin sheet of the present invention is not particularly limited, but is preferably 1 to 20% by mass, more preferably 1 to 10% by mass.

[0138] The resin sheet of the present invention may be one generally called a "sheet" having a thickness of 250 μm or more, one generally called a "sheet" having a thickness of 250 μm or less, or one generally called a "foil." In other words, the thickness of the resin sheet of the present invention is not particularly limited and may be appropriately selected depending on the period of use, the environment of use, the state of use, etc.

[0139] When the resin sheet of the present invention is used as a wavelength conversion sheet for agricultural use, the thickness of the resin sheet of the present invention is preferably 10 to 150 μm, for example.

[0140] The resin sheet of the present invention may contain, as needed, a spreading agent, agricultural materials, pesticides, biostimulants, inorganic substances such as silica, and the like.

[0141] The resin sheet of the present invention is suitably used as an agricultural sheet.

[0142] The present invention will be described in detail below based on specific examples, but the present invention is not limited to these.

[0143] [Example 1] Direct Synthesis Method: 1 mL of oleic acid and 10 mL of octadecene were weighed into a degassed 25 mL four-neck flask and stirred under reduced pressure for 5 minutes. Then, 271.3 mg of cesium carbonate was added and heated at 120°C for 1 hour while degassing to obtain solution (2a). Meanwhile, a 50 mL four-neck flask was degassed, and 1 mL of oleic acid, 1 mL of oleylamine, and 5 mL of octadecene were added and stirred for 5 minutes while degassing. Then, 25.3 g of tin iodide and 142.3 g of germanium bromide were added (Sn:Ge = 1:9), and the mixture was heated again at 120°C for 1 hour while degassing to obtain solution (1a). Next, solution (1a) was heated to 240°C while N ２ 0.85 mL of solution (2a) heated to 120 °C was injected, and 30 seconds after the total amount was added, the mixture was quenched in ice water to terminate the reaction, and the reaction mother liquor was obtained (Figure 2). Reprecipitation washing with a poor solvent and drying under reduced pressure allowed the Cs to separate without aggregation. ３ (Sn ０．１ Ge ０．９ ) (Br ０．９２ I ０．０８ ) ５ A solid powder of Sn / Ge halide nanocrystals with the composition was recovered. Transmission electron microscope (TEM) measurements confirmed that the average particle size was approximately 100 nm. In the solid powder state, the nanocrystals emitted broad orange light with a peak at 633 nm and a half-width of 143 nm, and exhibited a fluorescence quantum yield of 39% (Figure 3).

[0144] [Example 2] Direct Synthesis Method The same procedure as in Example 1 was carried out, except that the molar ratio of tin iodide and germanium bromide added was Sn:Ge = 2:8 in atomic terms, to obtain a reaction mother liquor (Fig. 2). As in Example 1, Cs was obtained without aggregation by reprecipitation washing using a poor solvent and drying under reduced pressure. ３ (Sn ０．２ Ge ０．８ ) (Br ０．７９ I ０．２１ ) ５A solid powder of Sn / Ge halide nanocrystals with the composition was recovered. Transmission electron microscope (TEM) measurements confirmed that the average particle size was approximately 100 nm. In the solid powder state, the nanocrystals emitted broad orange light with a peak at 674 nm and a half-width of 170 nm, and exhibited a fluorescence quantum yield of 44% (Figure 3).

[0145] [Example 3] Direct Synthesis Method: 1 mL of oleic acid and 10 mL of octadecene were weighed into a degassed 25 mL four-neck flask and stirred under reduced pressure for 5 minutes. Then, 271.3 mg of cesium carbonate was added and heated at 120°C for 1 hour while degassing to obtain solution (2a). Meanwhile, a 50 mL four-neck flask was degassed, and 1 mL of oleic acid, 1 mL of oleylamine, 1 mL of trioctylphosphine, and 5 mL of octadecene were added and stirred for 5 minutes while degassing. Then, 25.3 g of tin iodide and 199.8 g of germanium iodide were added (Sn:Ge = 1:9), and the mixture was heated again at 120°C for 1 hour while degassing to obtain solution (1a). Next, solution (1a) was heated to 240°C while N ２ The reaction mixture was cooled to 120°C and 0.85 mL of solution (2a) was injected. After 30 seconds, the mixture was cooled by quenching in ice water to terminate the reaction. The reaction mother liquor was obtained. The Cs ３ (Sn ０．１ Ge ０．９ ) I ５ A solid powder of Sn / Ge halide nanocrystals with the composition was recovered. Transmission electron microscope (TEM) measurements confirmed that the average particle size was approximately 77 nm (Figure 4). In the solid powder state, the nanocrystals emitted broad orange light with a peak at 688 nm and a half-width of 171 nm, and exhibited a fluorescence quantum yield of 65% (Figure 5).

[0146] [Example 4] Post-treatment method: 1 mL of oleic acid and 10 mL of octadecene were weighed into a degassed 25 mL four-neck flask and stirred under reduced pressure for 5 minutes. Then, 271.3 mg of cesium carbonate was added and heated at 120°C for 1 hour while degassing to obtain solution (2b). Meanwhile, a 50 mL four-neck flask was degassed, and 1 mL of oleic acid, 1 mL of oleylamine, and 10 mL of octadecene were added and stirred for 5 minutes while degassing. Then, 18.9 g of tin bromide and 142.3 g of germanium bromide were added (Sn:Ge = 1:9), and the mixture was heated again at 120°C for 1 hour while degassing to obtain solution (1b). Next, solution (1a) was heated to 240°C while N ２ The reaction mixture was cooled to 120°C and 0.85 mL of solution (2b) was injected. After 30 seconds, the mixture was cooled by pouring it into ice water to complete the reaction. ３ (Sn ０．１ Ge ０．９ )Br ５ A solid powder of Sn / Ge halide nanocrystals with the composition was recovered. Measurements using a transmission electron microscope (TEM) confirmed that the average particle size was approximately 45 nm. 0.4 mL of a hexane solution of oleylammonium iodide (OAmI) was added to 100 mg of the recovered solid powder of Sn / Ge halide nanocrystals, and the mixture was stirred at room temperature for 30 minutes. The resulting solid powder was then subjected to post-treatment to replace the halogen anions, resulting in the formation of Cs ３ (Sn ０．１ Ge ０．９ ) (Br ０．８２ I ０．１８ ) ５ A solid powder of Sn / Ge halide nanocrystals with the composition was obtained. The precipitate was collected by centrifugation, redispersed, and evaluated. In the solid powder state, it emitted broad orange light with a peak at 673 nm and a half-width of 167 nm, and the fluorescence quantum yield was 53% (Figure 6).

[0147] We also investigated powderization for the purpose of developing applications such as sheeting. The Sn / Ge halide nanocrystal reaction mother liquor obtained in Example 1 was powdered by washing twice with dimethyl carbonate, and performance evaluation was performed. Although there was a slight decrease in PLQY compared to the solution, the powder was successfully produced while maintaining a high PLQY (Figures 7 and 8). To confirm atmospheric stability, the nanocrystals were stored in air for five days, and it was confirmed that the emission wavelength remained constant even after five days of storage in air (Figures 9 to 11). The graphs in Figures 9 and 10 show the results for storage for one day, two days, three days, four days, and five days, respectively, from top to bottom.

Claims

1. The following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00) Sn / Ge halide nanocrystals are represented by the following formula:

2. A Sn / Ge halide nanocrystal composite comprising the Sn / Ge halide nanocrystal of claim 1 and a ligand bonded to the Sn / Ge halide nanocrystal, wherein the ligand has a lipophilic molecular chain and / or a hydrophilic molecular chain and a binding group.

3. A phosphor comprising the Sn / Ge halide nanocrystals according to claim 1.

4. A fluorescent material comprising the Sn / Ge halide nanocrystals according to claim 1 or the Sn / Ge halide nanocrystal composite according to claim 2.

5. A fluorescent material characterized in that the surface of the phosphor according to claim 3 or the fluorescent material according to claim 4 is coated with a light-transmitting resin.

6. A resin sheet comprising a light-transmitting resin substrate and containing the phosphor of claim 3 or the fluorescent material of claim 4.

7. A hot injection method is used to mix and react a solution obtained by mixing tin bromide and / or tin iodide, germanium bromide and / or germanium iodide in a solvent with a solution obtained by mixing a cesium precursor in a solvent, to obtain a compound represented by the following general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) A method for producing Sn / Ge halide nanocrystals, comprising a nanocrystal synthesis step (A) for obtaining Sn / Ge halide nanocrystals represented by the formula (wherein α1 is 0.00 to 0.40 and β1 is 0.00 to 1.00), wherein, among all raw materials mixed in the nanocrystal synthesis step (A), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, and the molar ratio of Br to the total of Br and I (Br / (Br+I)) is 0.00 to 1.00, on an atomic basis.

8. A solution obtained by mixing tin bromide and germanium bromide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted by a hot injection method to obtain a compound represented by the following general formula (2): Cs ３ (Sn α２ Ge （１－α２） )Br ５ (2) (wherein α2 is 0.00 to 0.40), a nanocrystal synthesis step (B) of obtaining Sn / Ge halide nanocrystals represented by the general formula (2) and a salt of a metal cation or an organic cation and an iodine anion, and a halogen substitution reaction is carried out to obtain a Sn / Ge halide nanocrystal represented by the general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (C) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in all raw materials mixed in the nanocrystal synthesis step (B), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, on an atomic basis; and in the halogen substitution step (C), the ratio (I / Br) of the number of moles of I in atom equivalent in a salt of the metal cation or organic cation and iodine anion to the number of moles of Br in atom equivalent in the Sn / Ge halide nanocrystals represented by the formula (2) is 0.00 to 5.

00.

9. A solution obtained by mixing tin iodide and germanium iodide in a solvent and a solution obtained by mixing a cesium precursor in a solvent are mixed and reacted by a hot injection method to obtain a compound represented by the following general formula (3): Cs ３ (Sn α３ Ge （１－α３） ) I ５ (3) (wherein α3 is 0.00 to 0.40), a nanocrystal synthesis step (D) of obtaining Sn / Ge halide nanocrystals represented by the general formula (3) and a salt of a metal cation or an organic cation and a bromine anion, and by a halogen substitution reaction, obtaining Sn / Ge halide nanocrystals represented by the general formula (1): Cs ３ (Sn α１ Ge （１－α１） ) (Br β１ I （１－β１） ) ５ (1) (wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00), and a halogen substitution step (E) for obtaining Sn / Ge halide nanocrystals represented by the formula (1), wherein α1 is 0.00 to 0.40, and β1 is 0.00 to 1.00; in all raw materials mixed in the nanocrystal synthesis step (D), the molar ratio of Sn to the total of Sn and Ge (Sn / (Sn+Ge)) is 0.00 to 0.40, on an atomic basis; and in the halogen substitution step (E), the ratio (Br / I) of the number of moles of Br in an atomic basis in a salt of a metal cation or an organic cation and a bromine anion to the number of moles of I in an atomic basis in the Sn / Ge halide nanocrystals represented by the formula (3) is 0.00 to 5.00.

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